The present invention is directed, in general, to computer networks and, more specifically, to a system and method that provides for anonymous transmission of electronic mail (xe2x80x9ce-mailxe2x80x9d) over a network and filtering of incoming e-mail based, at least in part, on the destination address of the e-mail.
In recent years, the availability of more efficient, reliable and cost-effective computers and networking tools has allowed many companies and individuals (collectively, xe2x80x9cusersxe2x80x9d) to become involved in an ever-growing electronic community. The immeasurable gains in technology experienced by the computer industry overall have allowed these users to rely on commercially available computers, such as personal computers (xe2x80x9cPCSxe2x80x9d), to meet their information processing and communication needs. To that end, PC manufacturers allow users to equip most PCS with an interface (such as a modem) that may be used for communication over networks, such as the Internet. The Internet is a well-known collection of networks (e.g., public and private voice, data, video and multimedia networks) that cooperate using common protocols to form a worldwide network of networks.
Cooperation often includes the communication of electronic mail (xe2x80x9ce-mailxe2x80x9d) from one user (a xe2x80x9csenderxe2x80x9d) to another (a xe2x80x9crecipientxe2x80x9d). One conventional e-mail protocol employed over the Internet, Standard Mail Transfer Protocol (xe2x80x9cSMTPxe2x80x9d), mandates that each e-mail message body have a header that includes the sender""s e-mail address (a xe2x80x9csource addressxe2x80x9d) and the recipient""s e-mail address (a xe2x80x9cdestination addressxe2x80x9d). All well-known e-mail protocols mandate inclusion of a source address to allow the recipient to send e-mail back to the sender.
Privacy has become a primary concern in today""s computer-based society. Users want to be able to express themselves in words, sounds or pictures over a computer network, but may not want to be identified as the source. In particular, users want to keep their true identity secret, but still wish to receive e-mail addressed to them. This need for privacy spans the spectrum of communication, from business transactions to personal thoughts. Unfortunately, mandated inclusion of the source address with the sender""s e-mail gives away the sender""s identity, compromising privacy.
One solution to this problem is a so-called xe2x80x9canonymous remailer.xe2x80x9d An anonymous remailer is a computer system, coupled to the network, that allows bidirectional e-mail communication over the network without compromising the sender""s identity. The recipient cannot discover the true identity of the sender unless the sender encloses identifying information in the body of the e-mail message itself.
Anonymous remailing is well known in the art. The most famous Internet remailer to date has been the Finnish xe2x80x9canon.penet.fixe2x80x9d remailer, which, at its zenith, boasted more than 500,000 users.
To support bidirectional e-mailing, conventional remailers must maintain a translation table that correlates real user addresses and alias source addresses (usually taking the form xe2x80x9cxxxxxx@remailer.addressxe2x80x9d). Upon receipt of a message from an anonymous sender, the remailer replaces the sender""s real source address with a corresponding alias source address and remails the message to the intended recipient. The recipient can reply to the message, but only by using the anonymous sender""s alias source address. Upon receipt of a reply from the recipient, the remailer substitutes the anonymous sender""s real source address for the alias source address and remails the reply to the anonymous sender.
The main problem with conventional remailers is the translation table itself. Because the table contains detailed real source addresses and the correlations between such real source addresses and alias source addresses, both hackers and law enforcement agencies covet it. Thus, the person maintaining the remailer must both protect the translation table from hackers and face thorny legal questions about the privacy of the senders who trust him to protect their true identity.
Even though a sender may preserve his anonymity by using an anonymous remailer, he still may be subjected to receiving a barrage of unsolicited, usually computer-generated e-mail (xe2x80x9cjunkxe2x80x9d e-mail or xe2x80x9cspam,xe2x80x9d in today""s Internet parlance), because the sender still may be reached via his alias source address. Currently, the only automatic way to protect against such unsolicited e-mail is to filter based on the source address contained in the header or specific words contained in the body. Unfortunately, filtering based on source address or words in the body of the message is crude at best, risking both the unintended deletion of valid e-mail messages and unintended retention of junk. Of course, manual filtering remains an option, but at the cost of time and with the risk of exposure to any offensive subject matter contained in such e-mail messages.
Therefore, what is needed in the art is an improved remailer, a method of remailing and a more effective way to filter unsolicited e-mail messages automatically.
To address the above-discussed deficiencies of the prior art, the present invention introduces a system for and method of, generating an alias source address for an electronic mail (xe2x80x9ce-mailxe2x80x9d) message having a real source address and a destination address and a computer network, such as the Internet, including the system or the method. In one embodiment, the system includes an alias source address generator that employs the destination address to generate the alias source address. The system further includes an alias source address substitutor that substitutes the alias source address for the real source address. This removes the real source address from the e-mail message and thereby renders the sender, located at the real source address, anonymous. The system further includes an e-mail forwarder that receives e-mail addressed to the alias source address, computes the real source address, and forwards the e-mail to the real source address.
The sender is therefore provided with a set of alias source addresses that may, in some embodiments of the present invention, be unique to each destination address. However, since the system automatically provides generation and substitution of source addresses, the user is freed of the task of tracking multiple alias source addresses.
In one embodiment of the present invention, the alias source address includes an encrypted version of the real source address, among other information. In this way, the e-mail forwarder can compute the real source address given the alias source address without any need for a translation table from alias source addresses to real source addresses. Another advantage of this embodiment is that the alias generator does not have to communicate with the e-mail forwarder. Thus the system may comprise any number of alias generators and any number of e-mail forwarders. Alias generators and e-mail forwarders may be added and removed from the system at any time.
In one embodiment of the present invention, the system further includes an e-mail filter capable of filtering incoming reply mail based on the alias source address. By causing the alias source address to depend upon the destination address, a single sender can have a set of different alias source addresses, allowing the sender to filter incoming reply mail, if he so desires, based upon alias source address. Purveyors of junk e-mail can obscure their identity or the content of an unwanted message by many means, but if they want to send e-mail successfully to that sender, they must address it to the sender""s exact same alias source address. The alias source address, when thus used as a destination address, provides users an effective way to filter junk e-mail and to determine, if they so desire, where the junk e-mail purveyor obtained the alias source address.
The ability to filter e-mail based on the alias source address is independent of the particular method of generation of the alias source address. To allow e-mail filtering by this method, the alias source address should depend upon the destination address. The alias source address generator may advantageously have one or more of the following three attributes: (1) consistency (the same alias is presented to the same destination), (2) uniqueness (the probability is low that two destinations are given the same alias) and (3) privacy (the recipient cannot determine the real source address given the alias source address).
In one embodiment of the present invention, the system takes the form of a remote anonymous remailer with which the sender must communicate over a network. In an alternative embodiment, the system executes locally on the sender""s computer. As the sender generates e-mail messages, alias source addresses are determined and added, eliminating a need for the remote anonymous remailer.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.